When a fabric garment is worn, soil and/or oily materials tend to accumulate and settle on and among the fibers of the fabric. Soiled garments are often cleaned under domestic laundry conditions, i.e., using laundry detergent formulations in aqueous solutions. Previously, oily soil would have been removed using very hot (typically 60° C.-90° C.) wash conditions, however, the current trend is to save energy by washing laundry at much lower temperatures, i.e., in the region of 15° C.-50° C. Unfortunately, however, oily soil is not easily removed at this temperature.
The development of laundry formulations which are capable of cleaning soiled fabric garments at lower temperatures (e.g., 15° C.-50° C.) is an ongoing endeavor and has led to laundry formulations containing a variety of additives including, but not limited to, dispersants, film formers, emulsifiers, surfactants, and builders. Certain polycarboxylate polymers, such as partially hydrolyzed acrylamide polymers and certain copolymers of methacrylic acid with ethyl acrylate, are very effective soil-release agents at low levels on the fabric.
For example, a polycarboxylate polymer in an aqueous acidic solution having a pH of less than 3 is described in U.S. Pat. No. 3,912,681 as capable of imparting non-permanent soil-release characteristics to cotton and cotton-blend fabrics. It is necessary to include a mineral acid in the aqueous solution to bring the pH below 3 and facilitate application of the polycarboxylate polymer. Thus, the technology disclosed in U.S. Pat. No. 3,912,681 is not suitable for consumer use, nor is it compatible with laundry detergent formulations which typically have a pH greater than 8.5.
U.S. Pat. No. 6,451,756 describes hydrophobically modified polycarboxylate polymers that are useful for promoting soil release on cotton and cotton blend fabrics under typical household laundry washing conditions, i.e., in aqueous solutions at temperatures between 15° C. and 50° C.
Another class of soil-release agents is alkyl or hydroxyalkyl cellulose derivatives. For example, as described in U.S. Pat. No. 4,136,038, methylcellulose compounds have been known for decades as successful soil release agents in laundry detergents.
The U.S. Pat. No. 4,000,093 discloses laundry detergents which comprise from 0.1% to 3%, by weight, of alkyl-, hydroxyalkyl-cellulose or alkylhydroxyalkyl-cellulose, and also from 5% to 50%, by weight, of surfactant which consists substantially of C10-C13-alkyl sulfate and has up to 5% by weight of C14-alkyl sulfate and fewer than 5% by weight of alkyl sulfate having alkyl radicals of C15 and higher.
U.S. Pat. No. 7,316,995 describes laundry detergents or cleaning formulations containing a water soluble builder system combined with cellulose derivatives which improve the soil release properties of fabrics. Cellulose derivatives suitable for use in the technology described in U.S. Pat. No. 7,316,995 include alkyl and hydroxyalkyl cellulose derivatives.
Mixtures of soil release agents with other additives for soil removal have also been proposed. For example, U.S. Patent Application Publication No. US 2009/0110870 A1 describes a soil resist additive comprising a mixture of at least one soil resist agent which is one or more fluorinated polyurethane, fluorinated acrylate or fluorinated methacrylate, and at least one additive which is maleic anhydride.
However, despite the extensive research activity in this field, there remains a need for a soil release additive which has superior soil release properties, especially oil- and grease borne soil, and which is highly effective on natural fabrics such as cotton, and cotton-blend fabrics, as well as synthetic fabrics such as polyester, and polyester-cotton fabrics, at low temperatures under domestic laundry conditions.